1. Anionic type:Hydrophilic groups are negatively charged, such as sulfates (e.g., sodium dodecyl sulfate).SDS), sulfonates (sodium dodecylbenzenesulfonate). Known for their strong cleaning power and abundant lather, they are relatively more irritating and were key components in soaps and early detergents.
2. Cationic type:Hydrophilic head groups are positively charged, primarily consisting of quaternary ammonium salts (such as benzalkonium chloride). They are characterized by strong bactericidal properties but are generally incompatible with anionic surfactants and exhibit relatively high irritation. They are commonly used in disinfectants and hair conditioners (where they neutralize the negative charge of hair to combat static electricity).
3. Zwitterionic type:A molecule containing both positive and negative charges, such as the betaine type,R-N+(CH3)2-COO-and amino acid types. They are characterized by extremely low irritation, high tolerance to hard water, and excellent compatibility.pHIt can exhibit both anionic and cationic properties under different conditions and is often used as a co-surfactant to reduce the irritation of formulations.
4. Non-ionic:Hydrophilic heads are non-ionic, such as fatty acid glycerides, sucrose esters, and alkyl polyglucosides.APG), fatty alcohol polyoxyethylene ether (AEO) etc. It is characterized by being mild, low-foaming, and highly stable, with its performance significantly affected by temperature (exhibiting a cloud point phenomenon). It is widely used in high-end facial cleansers, lotions, and industrial additives.
In nanomedicine formulations (such as drug delivery systems and nanomaterials), surfactants play an indispensable role. Their primary functions include:
- As a template or stabilizer:During the synthesis of nanoparticles, adsorption onto the particle surfaces is utilized to prevent agglomeration and control their size and morphology through steric hindrance or electrostatic repulsion.
- Forming micelles as carriers:When surfactants reach their critical micelle concentration, the micelles formed have a hydrophobic core that can encapsulate poorly soluble drugs or functional molecules, enabling solubilization and targeted delivery.
Regarding safety considerations, particular attention must be paid in pharmaceutical and cosmetic applications:
- Biocompatibility:Choose natural or low-irritant surfactants (such as lecithin, sucrose esters, poloxamers) to avoid causing hemolysis or cytotoxicity.
- Inner Destiny:Consider the metabolic, degradation, and excretion pathways of surfactants in the body to ensure that both the surfactants and their degradation products are non-toxic and harmless.
- Regulatory Compliance:It is essential to adhere to the regulations and limits for the use of surfactants in relevant fields, such as pharmaceuticals, cosmetics, and food.